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Chapter 8- An introduction to Metabolism - Coggle Diagram
Chapter 8- An introduction to Metabolism
8.1-An organism’s metabolism transforms matter and energy
Metabolic pathways-
-specific molecule is altered is a series of defined steps.
Enzymes-
- Macromolecule that speeds up chemical reactions.
Catabolic Pathways
- Breakdown complex molecules-> simpler compounds ex- cellular respriation
Anabolic Pathways
- consume energy to build complex molecules from simpler ones.
Energy flow-
-energy released from catabolic pathways can be stored to drive catabolic pathways.
Bioenergetics
-- study of how energy flows through living organisms.
Metabolism-
Totality of organism's chemical reactions.(emergent property)
Forms of energy:
- Kinetic ( movement), Thermal(temp), Potential( energy matter posses due to location or structure), chemical energy( chemicals), photosynthesis( plants convert light into energy)
The laws of transformation:
study of energy transformations in matter.
1st law-energy can be transferred and transformed but cannot be created or destroyed.
2nd- every energy transfer or transformation increases the disorder of the universe.
Types of systems-
Isolated:
no exchange of energy transformations in matter.
Open systems-
energy and matter can be transferred between the systems
Energy Conservation:
Energy is never created nor destroyed.
Entropy:
measure of molecular disorder or randomness.
Spontaneous processes
: processes increase entropy and require input of energy. EX: H2O flowing downhill
Non spontaneous processes-
- Processes that decrease entropy and require input of energy. EX:H2O begin pumped uphill
Concept 8.2: The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously
Free-Energy Change, ΔG
Gibbs free energy -
function that represents the portion of a system's energy that can perform work
Equation: ΔG = ΔH − TΔS
ΔH = change in enthalpy (total energy)
T = absolute temperature (Kelvin)
ΔS = change in entropy (disorder)
Negative ΔH (releases energy) or positive ΔS (increases disorder) → ΔG becomes negative.
Free energy = system’s instability → tendency to change to a more stable state.
At equilibrium:
Forward and reverse reactions balance.
Systems move toward equilibrium (spontaneous) but never away from it (nonspontaneous).
At equilibrium → ΔG = 0 → no work done.
Living cells must stay out of equilibrium to stay alive.
Exergonic Reactions (“energy out”)
ΔG < 0 → releases free energy → spontaneous
Endergonic Reactions (“energy in”)
ΔG > 0 → requires input of energy → nonspontaneous
Energy in Ecosystems
Plants capture solar energy → convert to chemical energy → store in glucose.
Animals use organic molecules from plants → extract free energy via exergonic reactions (like respiration).
All organisms are open systems exchanging energy and matter with surroundings.
Concept 8.3: ATP & Energy Coupling
Types of cellular work
Chemical Work – pushing endergonic reactions ( polymer synthesis).
Chemical Work
Phosphorylation – ATP transfers a phosphate group to another molecule → phosphorylated intermediate.
Transport Work – pumping substances across membranes against gradients.
Transport Work
ATP phosphorylates transport proteins, changing their shape → moves solutes against gradients.
Mechanical Work – movement (cilia beating, muscle contraction, chromosome separation)
Mechanical Work
Motor proteins use ATP binding & hydrolysis to “walk” along cytoskeletal tracks.
ATP (Adenosine Triphosphate) =
Adenine (nitrogen base) + Ribose (sugar) + 3 Phosphate groups.
Hydrolysis of ATP-Used for cellular work, exergonic( muscle contraction)
Exergonic reaction → releases free energy.
ATP Regeneration- From catabolism or light, endergonc.( Cellular respiration or photosynthesis)
ATP Cycle-
Couples exergonic & endergonic reactions
Transfers energy within cell
ex: Entire metabolism
Concept 8.4- Enzymes Speed Up Reactions by Lowering Energy Barriers
Enzymes = proteins that act as catalysts; speed up reactions without being used up.
Activation Energy (Eₐ)
Energy needed to start a reaction.
Enzymes lower this energy so reactions happen faster.
How enzymes work
Substrate binds to the enzyme’s active site.
They form an enzyme–substrate complex.
Enzyme may slightly change shape (induced fit) to hold substrate tighter.
Reaction happens → bonds break or form.
Products release, and the enzyme is ready to be used again.
Factors that affect enzymes: temp, ph, concentration, inhibitors
Regulation in the Cell
Cells control enzymes to manage metabolism.
Allosteric regulation: molecules bind to a site (not the active site) to turn enzyme on or off.
Feedback inhibition: product of a pathway shuts off the first enzyme when enough product is made
Concept 8.5 – Regulation of Enzyme Activity Helps Control Metabolism
Allosteric Regulation
Enzyme activity is controlled by molecules binding at a site other than the active site.
Allosteric Activation and Inhibition
Active form (works), Activator → stabilizes the active form.
.
Inactive form (doesn’t work). Inhibitor → stabilizes the inactive form.,
Cooperativity
A special kind of allosteric regulation.
When one substrate binds to an enzyme, it makes other sites more active.
Feedback Inhibition-The end product of a metabolic pathway shuts down the first enzyme in the pathway.
ex Isoleucine synthesis: When enough isoleucine is made, it binds to the first enzyme and stops the process.
Localization of Enzymes- Enzymes are organized in specific locations in the cell to work efficiently.